Liquid crystal display devices are thin and light, with low power consumption. By virtue of these features, they are used in various technical fields as displays for televisions and office automation equipment such as personal computers. In recent years, liquid crystal display devices have been used for mobile devices such as cellphones, for vehicle-mounted equipment such as satellite navigation devices, and for tablet computers and signage.
A memory-in-pixel (MIP) liquid crystal display device is known in which pixels include respective memories capable of storing data. In the MIP liquid crystal display device, in the case where an image is displayed using data held in memories, an operation for writing an image signal does not need to be performed in cycles of a frame period, and thus the power consumption can be reduced.
It should be noted that in a liquid crystal display device, for example, when an electric field is applied to a liquid crystal layer, the alignment state of liquid crystal molecules is changed to also change the transmissivity, and an image is thus displayed. However, in the case of adopting a direct-current driving in which the polarity of a voltage to be given is not changed, an electric-field distribution is changed because of the presence of impurity ions in a liquid crystal layer, thus reducing the display quality of an image. Therefore, in general, an alternating-current driving is adopted in which the polarity of the voltage to be applied is inverted at regular intervals.
In the MIP liquid crystal display device, in the case where an image is displayed using data held in memories, as an alternating-current drive scheme, a line-inversion drive scheme is used in which the polarity of a voltage to be applied is changed in units of one horizontal period. However, the MIP liquid crystal display device is also required to further reduce the power consumption.